This invention relates to bead wetting angle detection and control. More specifically, this invention relates to a method and system using optical profilers for quality control of a bead.
When performing an automated welding process, the bead wetting angle is a significant factor in determining the fatigue strength of a weld joint. If the wetting angle is too high, the likelihood of fatigue cracks is increased.
Although various feedback control systems have been used to control automated welding processes, such feedback control systems have generally been subject to one or more of several disadvantages. For example, some such systems have used 2D vision sensors directed toward the molten weld pool. Although knowledge about the weld pool is useful, it is not usually sufficient to determine some important characteristics of the bead which results after hardening of the weld pool. Other arrangements have used infrared or visible radiation detectors for sensing temperatures and temperature gradients of a newly-laid bead in order to determine the width of the weld bead or the severity of the metallurgical quench. Such radiation detection processes are often subject to error in the measurements because of variations in the surface conditions which may significantly affect apparent temperature gradients.
U.S. Pat. No. 4,724,302 filed in the name of Carl M. Penney and Michael H. McLaughlin issued on Feb. 9, 1988, assigned to the assignee of the present application, and hereby incorporated by reference, discloses an arrangement for control of bead processes such as welding and application of sealant or glue. A feedback control process is used in order to maintain the height, width, and/or cross sectional area of the bead satisfactorily.
Although stabilization of height, width, and area of a bead is useful, this does not necessarily maintain the bead wetting angle to a prescribed range. Moreover, knowledge of the height, width, and area of a bead would not necessarily allow one to know the bead wetting angle. Further, accurate measurement of the bead wetting angle usually requires a higher resolution than obtained from optical profilers which view the complete width of the bead, such as the optical profilers used in the above patent.